The present invention relates to an image processing method and apparatus, and more particularly to a method and apparatus for conducting anisotropic diffusion filtering on a two-dimensional image.
Filtering techniques that can remove noise from a two-dimensional image without a side effect such as edge degradation, include anisotropic diffusion filtering.
The anisotropic diffusion filtering comprises: finding pixel differential values with respect to nearest surrounding pixels for each pixel, finding conduction coefficients for each pixel based on a pixel value gradient, and using the conduction coefficients and pixel differential values to calculate a pixel value in an output image according to a predefined calculation formula.
The calculation formula is of a scale-space type, in which the calculation result in one pass is used as an input to the next pass and the calculation is repeated a plurality of times. As the calculation is repeated more times, noise is incrementally reduced (for example, see Non-Patent Document 1).
[Non-Patent Document 1]
Pietro Perona, et al., Scale-Space and Edge Detection Using Anisotropic Diffusion, IEEE Transactions on Pattern Analysis and Machine Intelligence (U.S.), Vol. 12, No. 7, pp. 629-639, 1990.
Such anisotropic diffusion filtering involves finding the pixel value gradient for each pixel and saving it once as a two-dimensional distribution image, reading the pixel value gradient from the two-dimensional distribution image to calculate the conduction coefficients, and then calculating the pixel value in the output image using the coefficients and pixel differential values, and conducts such processing on a pixel-by-pixel basis, resulting in a long time and slow operation.